[unreadable] [unreadable] Group drug counseling is the primary treatment modality used in community settings for the treatment of cocaine dependence, as well as alcohol and most other substances of abuse. Despite the prevalence of this modality, and data on the efficacy of group approaches to the treatment of substance use disorders, little is known about how the treatment works to achieve positive outcomes. Thus, as described in the RFA, research is needed on the mechanism of action of group treatments for substance abuse. Drawing upon research on individual drug counseling and on group therapy for non-substance abuse problems, we propose to examine several theoretically important therapy process variables as predictors of the outcome of group drug counseling for cocaine dependence. Specifically, we propose to examine degree of patient participation, quality of participation, quality of the therapeutic alliance, and frequency of feedback (and positive feedback), as assessed in group drug counseling sessions, as predictors of treatment outcome. Furthermore, the relation of these process variables to two potential mediators of changes in drug use (changes in beliefs about drug use and endorsement of 12-step philosophy) will be examined. Group drug counseling sessions will be drawn from an archival tape collection from the NIDA Cocaine Collaborative Treatment Study (NIDA CCTS, Crits-Christoph et al., 1999). A second aim of the current proposal is to develop a novel approach to the analysis of group therapy data. Research on the mechanism of group counseling has been hindered by a variety of difficulties in studying treatments delivered in group formats. In particular, statistical analyses of studies using group therapy/counseling needs to address the inherent clustering within the data (i.e., there is an issue of non-independence of observations within a group). While statistical techniques such as mixed-effects models and generalized estimating equations exist for handling clustered data arising in group therapy studies with traditional static group designs, in the real world drug counseling groups typically have a "rolling" or "dynamic" structure, meaning that new members are added on an ongoing basis and existing members dropout over time. Statistical solutions for addressing such "rolling" groups have yet to be developed. Our second aim is to develop a new statistical approach to the analysis of data from "rolling" groups. [unreadable] [unreadable]